Objectives: To evaluate the effect of immediate dentin sealing and optical powder removal method on the fracture resistance of CAD/CAM-fabricated ceramic endocrowns. Materials and methods: Seventy-eight extracted premolars were endodontically treated. Standardized endocrown preparations were done in 60 teeth. Teeth were divided equally (n = 10) depending on the treatment of dentin (delayed sealing [DS] or immediate sealing [IS]), and the methods of optical powder removal (air-water spray washing [AW]; microabrasion [MA]; or aqueous suspension of pumice [PB], followed by air-water spray washing). After cementation, specimens were thermocycled (5,000 cycles, 5°C/50°C) and stored in distilled water for 1 week. Specimens were loaded in compression using a universal testing machine until failure. Failure load was recorded, and modes of failure were examined under a stereomicroscope. Micromorphological evaluation of different dentin treatments was done under SEM (n = 3). Results were analyzed using two-way ANOVA and Bonferroni post hoc multiple comparison tests (α = 0.05). Results: Fracture resistance of all IS groups was significantly lower than DS groups, except for AW. There was no statistically significant difference between powder removal methods. Conclusion: Immediate dentin sealing does not improve the fracture resistance of endocrown restorations. Air-water spray washing is adequate to remove the optical powder after optical scanning impression taking. Keywords: adhesion, endocrown, immediate sealing, fracture resistance